The present invention relates to a method of coding a sequence of segmented images comprising a plurality of regions and associated labels and defining successive partitions, said method comprising the operations of estimating a motion model that characterizes for each of said regions the evolution of the segmentation from a previous partition to the current one and encoding the contour and the texture of each region of said current partition.
The invention also relates to a system for coding a sequence of segmented images comprising a plurality of regions and associated labels and defining successive partitions, said system comprising means for estimating a motion model that characterizes for each of said regions the evolution of the segmentation from a previous partition to the current one and means for encoding the contour and the texture of each region of said current partition, and to a coded signal as obtained at the output of such a system and to a storage medium for storing said coded signal.
The invention also relates to a method of decoding coded signals corresponding to the regions of each successive partition of a sequence of segmented images, and to a decoding system for carrying out said decoding method.
In the following description, the word "image" has to be understood according to its widest meaning. It is indeed clear that the invention deals not only with conventional images in which at least a luminance signal is associated to each picture element (or pixel), but also more generally to any set of tridimensional data (u, v, w) among which two of them define a kind of position within a predetermined frame and the third one a value varying within a given range and respectively associated to each pair of data. The proposed method offers however a substantial interest for all segmentation-based coding techniques and can be used particularly in video terminals that use a motion compensated coding of the partition issued from the segmentation. Such techniques are mainly useful for very low bit rate applications, and a standardization under the reference MPEG4 is contemplated (MPEG is an acronym for "Moving Picture Experts Group", which is a group of experts of the International Standardization Organization ISO).
The document "A high-compression image coding method based on a new segmentation technique", L. H. Chen and Y. K. Chen, Proceedings of the National Science Council, Republic of China, Part A: Physical Science and Engineering, vol. 16, n.degree.5, September 1992, pp.403-421, relates to a segmentation based coding technique describing how to represent the regions obtained after having partitioned an input video sequence into regions. The described coding method includes a contour coding used to describe the contour points of each region and a texture coding used to estimate the value of each pixel in each region of the partition. A particular problem with such a technique is to maintain at a low level the computational load and the cost of transmission when the information to encode and transmit includes motion information both about the partition and the pixels inside each region of said partition.